feat(mcp): harden HTTP API client and routes

[ghshhf]

Summary

This PR enhances the MCP HTTP API with improved client error handling, additional routes for tool discovery, and test coverage updates.

This is the fourth in a series of split PRs (per maintainer feedback). See #10317 for the overall discussion.

Changes

• Modified: pkg/mcp/localaitools/httpapi/client.go

  • Improved error handling

• Modified: pkg/mcp/localaitools/httpapi/routes.go

  • Additional routes for tool discovery

• Modified: pkg/mcp/localaitools/coverage_test.go

  • Updated test coverage

Why Separate?

This is a self-contained, non-controversial change:

• No P2P/auth/cache complexity
• No dead code
• Improved MCP integration (used by AI agents)
• Test coverage updated

Follow-up PRs (from #10317)

1. ✅ PR 1: Config YAML endpoints (feat(config): add GET /api/models/config-yaml/:name endpoint #10318)
2. ✅ PR 2: Template/context pipeline (feat(templates): add TemplateLoader for context-aware template evaluation #10320)
3. ✅ PR 3: Metrics/monitoring additions (feat(metrics): add backend monitoring metrics and telemetry #10321)
4. ✅ PR 4 (this PR): MCP HTTP API routes/client hardening
5. PR 5: Reasoning parser (with tests)
6. PR 6: Distributed cache (with tests, cache invalidation docs)
7. PR 7: P2P node snapshot + ReplaceNodes (design doc, cancellation safety)
8. PR 8: Realtime ephemeral key (HMAC tests, userID binding)

Testing

• Verify MCP HTTP API client handles errors correctly
• Verify new routes work for tool discovery
• Run existing MCP tests

Related Issues

Part of #10317